🍕 Topics & explainers · 5 min read
Comparing fractions in Class 4: which slice is bigger?
How Class 4 children compare fractions — same denominator, same numerator, and unlike fractions — with the bigger-denominator trap from SOF IMO.
Comparing fractions is deciding which of two fractions is the bigger share — is 3/4 of a pizza more than 5/7 of it? Class 4 children meet three cases, each with its own quick rule, and olympiad questions love the third case, where neither the tops nor the bottoms match.
The idea in one minute
- Same denominator (bottom number): the bigger numerator wins — 5/8 > 3/8.
- Same numerator (top number): the smaller denominator wins, because the whole is cut into fewer, bigger pieces — 2/3 > 2/5.
- Neither matches: rewrite both with a common denominator, or compare each to an easy benchmark like 1/2.
- Picture it: a fraction is slices of one whole. More slices of the same size, or the same count of bigger slices, means more pizza.
✏️ Warm-up: same denominator
Which of these fractions is the greatest?
- A1/8
- B3/8
- C5/8
- D7/8
Show the answerAnswer: 7/8
Answer: 7/8. All four fractions have the same denominator, 8, so every piece is the same size — one eighth. More pieces means more: 7 eighths beats 5, 3 and 1 eighths. The greatest is 7/8.
✏️ Level up: same numerator
Which of these fractions is the greatest?
- A2/3
- B2/5
- C2/7
- D2/9
Show the answerAnswer: 2/3
Answer: 2/3. The numerators are all 2, so each fraction is two pieces — but the pieces are different sizes. Cutting a whole into 3 gives bigger pieces than cutting it into 5, 7 or 9. Two big pieces beat two small ones, so 2/3 is the greatest.
✏️ Olympiad twist: nothing matches
Which of these fractions is the greatest?
- A3/4
- B5/7
- C2/3
- D7/14
Show the answerAnswer: 3/4
Answer: 3/4. First simplify 7/14 = 1/2 — clearly the smallest here. For the rest, compare 3/4 and 5/7 with the common denominator 28: 3/4 = 21/28 and 5/7 = 20/28, so 3/4 is bigger. And 2/3 = 8/12 while 3/4 = 9/12, so 3/4 beats 2/3 as well. The greatest is 3/4.
Comparing fractions has its own ladder of levels in LittleMathematicians’s Class 4 Fractions topic — same-denominator questions first, and mixed comparisons like the last example once your child’s mastery is ready for them. It is free during early access if you would like to explore it together.
Practice this the fun way
Adaptive levels, exam-pattern mocks and progress you can see — free during early access.
Start free